1. Field of the Invention
The present invention relates to novel heterocyclic compounds exhibiting excellent antiulcer action.
2. Prior Art
Compounds which have gastroprotective action have been disclosed, for example, in U.S. Pat. No. 3,070,623 and U.S. Pat. No. 4,335,048. Moreover, compounds having a pyridopyrimidine ring are disclosed in U.S. Pat. No. 4,457,932 and EP. Pat. Publn. A-218,423.
Prior to the present application, the present inventors filed EP. Pat. Publn. A-218,423 disclosing serial compounds having a pyridopyrimidine ring with potent gastroprotective activities. Some of those have aromatic heterocyclic groups at the 9-position of the ring. On the other hand, the present invention involves, as an aspect, pyridopyrimidine-type compounds, some of which have also heterocyclic group. However, the heterocyclic groups of the present invention are aliphatic ones such as morpholinocarbonyl, piperazinocarbonyl or thiomorpholinocarbonyl, and therefore they differ from those of the prior art in this sense. Moreover, the compounds of the present invention are stabler in alkali and show more potent activities over a longer period of time.